My computer won't POST when I install my new video card

• Does the new video card work in another system?
• Is there an extra power-supply cable you're forgetting to connect (eg a 75W 6-pin PCIe connector)?
• Is your power supply capable? (The HD5770 system requirements show a 450W PSU with 6-pin PCIe connector is necessary, and provide a link to finding information on which PSUs are certified for use with ATI graphics cards.)

The system requirements do not seem to require PCIe 2.1, so you may be in the clear there (only a 16-lane (x16) PCIe slot is listed as required). Sometimes it's hard to tell if "supports" new-tech-version really means "requires".

I think problem might be in BIOS of your board.

I had very similar problem with MSI 945GCM5-F V2 and RadeonHD 5770. Then I read on some forum that it was due to misunderstanding between card PCIE version protocol and BIOS of MB. Guy from the forum requested updated BIOS from MSI support and they have send it to him.

I did the same and got BIOS that was perfectly able to POST with 5770. This BIOS was not on the site, only through MSI support channel.